One form of vertical joint system for a surface covering panel may include male and female parts. The male and female parts are formed along the sides of the panel. The male and female parts engage each other to join corresponding panels when moved toward each other in a direction perpendicular to a plane of the panels. When the panels are flooring panels this direction is a vertical direction. The male and female parts have surfaces that contact each other to arrest vertical separation of engaged panels.
One potential problem with vertical joint systems is “lipping”. Lipping occurs when the upper edge of one panel lifts from the upper edge of the adjoining panel. This creates a lip or step at the upper edges of adjacent joined panels. To assist in reducing lipping one practice is to provide the contacting surfaces of the male and female parts at the front end of the joints. The front end of the joint is the end closest to an upper edge of an upper surface of the panels. An example of this is shown in U.S. Pat. No. 7,552,568 in which the front end of a male part has a surface formed with a locking heal that contacts a locking surface formed on the surface at the front end of a female part. An alternate practice is to uses separately manufactured plastic inserts or clips that are fitted into the panels. However this adds to manufacturing costs and the insert/clips at times fall out of the panels during transport and handling.
The above description of the background art does not constitute an admission that the art forms the common general knowledge of a person of ordinary skill in the art. Further, the above description is not intended to limit the application of the vertical joint system.